Firstly, it’s no one’s business.
Secondly, whether we like it or not, despite the fact that it’s illegal, age discrimination DOES occur in the job market, so that’s another reason not to include it. Age discrimination in the job market can work both ways though. You can be seen as too old, or too young.
Yes, it’s illegal to discriminate based on age, but it happens. Don’t give the reader of your résumé an opportunity to make unfounded judgements about you based on your age. Focus on the value you bring to an employer, and your results (not the number of years of experience), remove graduation year dates from your qualifications (unless you are a new Grad or have a strategic reason to leave them in) and don’t use an email address that includes numbers that could be interpreted as your year of birth.